> I've just realised the answer: my stylesheet now includes a class
> called Glossary and I just use span class="glossary" in the HTML.
> (sigh)
That's generally the preferred, non-XML, way of extending HTML.
However, what you describe appears to be one the most classic uses
of hypertext, so I'd have to argue that the most standard way of
providing this function is with <a href..> elements.